How to Encrypt and Decrypt Files on an Android Device

Encrypting files on your Android device allows you to keep those files from being stolen, and even if they get stolen they would be unreadable as long as they are not decrypted using a proper key. What it does is present the file as garbled information, usually to an AES 128 or AES 256 standard that essentially makes the information impossible to decipher.

Here’s how to encrypt files on your Android device – whether you want to encrypt everything on your phone or just specified files.

Encrypt Everything on Your Android Device

The most comprehensive encryption method on Android is to do a full-disk encryption, which is a feature that’s handily baked into the operating system. This will lock your Android device behind a password and/or PIN and on weaker devices may cause some slowdown. The price you pay for security!

To do this, go to “Settings -> Security -> Encrypt phone.”

If you’re on Android 7.0 or higher, then you might find that this option isn’t there. An alternative location for this is “Settings -> Storage -> Phone storage encryption.”

Still, a third possibility is that you need to unlock developer options to encrypt your phone. To turn it on you’ll need to go to “Settings -> About -> Software information -> More,” then tap “Build number” seven times to unlock Developer options.

Under “Settings -> Developer” options you should now find the option to “Convert to file encryption.” Back up your data, though, because this will erase everything on your device and start fresh.

Encrypt Specific Files on an Android Device

In order to encrypt files on your device you are going to use an app called Andrognito that uses the 256-bit encryption algorithm to securely safeguard your files.

1. Head over to the Google Play store and download and install Andrognito on your device.

2. Launch the app.

3. When the app is launched for the first time you need to enter your name and a four-digit PIN that will safeguard your files. Do so and tap on the arrow to move forward.

4. Enter the four-digit PIN again to confirm it. Tap on the arrow icon to move forward.

5. For an extra layer of security it will ask you to create a security question. Type in the question and answer, and tap on the arrow icon to move ahead.

6. Here comes the part where you can create a vault to put your encrypted files in. Type in a name for the vault and a four-digit PIN. Tap on the pink icon, and you will move to the next screen.

7. You can now start adding files to the vault for encryption. Tap on the “+” icon on your screen and select either All Files, Images, or Videos to be encrypted.

8. Tap and hold on a file for the encryption option to show up. You can select multiple files to be encrypted all at once. When you are done selecting, tap on the lock icon given in the top-right corner to encrypt the selected files.

9. You should see the following orange icon on your screen when the files are successfully encrypted.

The selected files have been encrypted using a military-grade AES 256-bit encryption algorithm. If someone gets access to these files, they will not be able to read them unless they have the key that was used to encrypt the files.

If you wish to decrypt the files, you can do so using the same app.

Decrypting the Files

1. Launch the Andrognito 2 app from your app drawer.

2. Enter your four-digit PIN to access the safeguarded data.

3. You should be able to see all the files that you have encrypted so far. Tap and hold on the ones you wish to decrypt, then tap on the unlock icon given in the top-right corner. It should decrypt the selected files for you.

Your files are now decrypted, and they are no longer a part of your vault. They can now be accessed as normal files just like you were accessing them before.

Conclusion

While locking a file allows you to have an additional layer before someone can access your files, encrypting provides more protection, as it hides them behind an unbreakable code of nonsense. If you’d like to keep your files private, this is the best way to ensure that the only people to ever seen them will be the people you want to see them.

This article was first published in May 2015 and was updated in Nov 2017.

17 comments

I just use ZArchiver to encrypt files or folders in encrypted 7z format. While I am not sure with the security of Andrognito 2 since it’s a new and untested encryption format, encrypted 7z files have been around for years and are known to be secure. I have been securing my files with encrypted 7z files which I store in the cloud.

Plus, encrypted 7z files has the advantage of being portable to desktop PCs and is supported by the most popular archivers (WinZip, WinRAR, 7-zip).

I want to encrypt file and store it in SD card. I want to decrypt that encrypted file and store it in SD card again. I have tried to encrypt file by opening as file stream and encrypt is but it is not working. I want some idea on how to do this.

Unless I’m missing something, I see a big problem with a 256-bit encryption system that is protecting itself, and its folders, with 4-digit PINs (and I do understand there is an additional security question). Therefore, the security of my encrypted folder is as good as a 4-digit password, which is basically a useless password.

To be useful (to me at least), the program log-in PIN needs to change to a password (as many as 32 characters, with 12 characters minimum), and to include any keyboard characters. I actually do use 32-character passwords on any account that allows that many.

For now, I’ll stick with AES’s Windows portable app. I have used apps from Microsoft and others (Omziff, DCU, TrueCrypt, …, etc.), but I like AES’s flexibility (choices / options of the encryption bits, 128, 192, 256, …, 448, with a choice of AES, Blowfish, or Serpent, but only Blowfish goes to 448-bit encryption), and its lightning speed. Each encrypted file is a stand-alone file, with its own password (although a password can be applied to a number of files, or all files, at the time of encryption). I use one password, over 45 charcters, for all my encryptions. AES app also allows for folder encryption.

The encrypted file(s) can be copied, moved, emailed, etc., on its own, and can be decrypted using the same app, as long as you know 2 things: -The password, and -The encryption used (128, 256, …, etc.), although this could be guessed by trial and error, as long the user doesn’t lock him/herself. All the above mentioned Windows apps are portable (no installation needed), and are free. Just my 2-cents.

It seems you’ve wholly encrypted your device and not using the app mentioned in the article. As for that, you need to decrypt it using appropriate tools or you can flash back the stock firmware and see if that works for you.

I have hidden some folders in Redmi2 prime phone..Now it is not visible and cant access.I have tried all options such as “show hidden folder” option..but nothing is working out.Please help me to retrieve original files back.

My company has developed an app for our customers which has several video lessons which are encrypted. The app decrypts the video and runs the video lessons. In some of the mobiles the encrypted videos do not get transferred and a message comes that your mobile will not be able to read the file. It seems like a security feature of the phone which treats these files as malaware and blocks the transfer. Is there some.solution to this problem?

Been using Cyptomator on Linux for a few weeks. It encrypts/decrypts folders – so anything you put in a folder is encrypted. So far, it’s been working well with a few gotcha’s – some applications have problems directly accessing (decrypted) files. This may have to do with the longer DAV-based link.

The authors have programs available for Android, iOS, the major desktops… another plus: since it encrypts an entire folder, it’s useful for online storage in places like dropbox, etc. This means that all files placed in an online folder are fully encrypted at ‘rest’. So far, I feel pretty comfortable with it’s behavior on Linux. Android testing will begin soon. I’m mostly interested in local encryption though.

I also want to know that I can simply copy an encrypted folder (or set of folders) anywhere and have faith that they’re available on the different platforms using Cryptomator to decrypt (and access) as necessary. It’s also very user-friendly – simply point Cryptomator to an encrypted folder and BOOM! Instant access.

i encrypted my messages without any app in my gionees6s and i have been looking for a way to decrypt the messages and i cant do that and right now the messages are very important to me please someone should hep out